1. Field of the Invention
The present invention pertains to apparatus for dispensing liquid and pulverulent materials, such as paint formulations, and in particular to apparatus for dispensing several products at the same time, into a common receptacle.
2. Description Of the Related Art
In various industries, such as the paint industry, for example, formulations of liquid or pulverulent components are routinely mixed in small batches or quantities. For example, in the retail paint industry, paint and other coatings are custom-mixed in relatively small quantities (e.g., 1 gallon or 5 gallon containers) for individual customers, on a demand basis. Today, paint and similar coatings are custom-mixed in a wide variety of retail establishments, such as paint and department stores, hardware stores, and home decorating centers. Custom blending or "tinting" of a paint or other coating material usually requires adding several components, such as small quantities of different colored tints, to a paint base. Typically, the tinting materials are dispensed directly into a container of paint base material, sequentially, one at a time.
In one popular type of dispenser, canisters of colorant material are arranged on a turntable and are indexed one at a time over a container of paint base material. Thus, a certain amount of time is required to index the color canisters, and if an operator is interrupted, a note must be made of the paint formulation steps which have already been completed, and those which need to be taken to complete the paint formulation.
Several attempts have been made over the years to automate the dispensing process. For example, computers have been provided with paint formulations stored in memory, with the steps required for a paint formulation being sequentially displayed to direct an operator. Such systems have required the operator to manually access a particular colorant canister called for by the computer program and to notify the computer that the dispensing step has been completed for each colorant called for in the formulation.
A number of so-called simultaneous dispense machines have been proposed to further automate the dispensing operation. For example, one machine has been offered for sale by the On Computer Electronics A/S of Copenhagen, Denmark. The machine is described in PCT Published Application No. WO 87/05697. A number of pump pistons are mounted atop a circular plate which is driven from below by a servomotor which drives the circular plate toward and away from an upper plate. Rotary valves are located atop the pistons to dispense a metered amount of fluid pumped by the piston. Multiple pistons disposed in a circle on the circular plate are simultaneously operated by the single servomotor with the rotary valves being operated for a particular pumping stroke to simultaneously dispense metered amounts of fluids. The pistons are individually mounted as discrete components on the circular plate, with the rotary valves carried directly on the pistons.
In another example of a simultaneous dispense machine, U.S. Pat. No. 4,946,100 to Peter Fleming and Robert Dee shows a system with multiple stages of dispensing actuation. A motor-driven screw shaft reciprocates a ball screw back and forth along the shaft axis. An actuating arm carried on the ball screw drives a piston rod so as to pressurize a hydraulic circuit. The hydraulic circuit drives a plurality of piston pumps arranged about a part-circular base plate. A series of valves directs pressurized flow to a dispense head. However, advances are still sought for automating the dispensing operation.